Load carrying unit



Aug- 23, 1966 J. E. RAPSON ETA.. 3,267,882

LOAD CARRYING UNIT Filed July 28, 1954 V l 24 j 25 :li/,26

7 /0 d J/v VENTO/Q5 Jl. RAPSON BJ. NICHOLSON BY P. N DENT @Win02, `m9bwm A T TOPNEY United States Patent O 3,267,882 LOAD CARRYING UNIT .lohn Edward Rapson and Brian John Nicholson, Southampton, and Peter Norman Dent, Hythe, England, assignor-s to Hovercraft Development Limited, London, England,a British company Filed July 28, 1964, Ser. No. 385,732 Claims priority, application Great Britain, July 31, 1963, 30,450/ 63 Claims. (Cl. 10S-51) This invention relates to units for supporting loads relative to a surface wherein the load is at least partly supported by a cushion of pressurised gas formed and contained between the unit and the surface or between the unit and the load or member carrying the load. The invention also relates to apparatus comprising three or more of such units attached to a load or to a platform for carrying that load, or to a series of such units positioned so that they remain fixed, the load moving over the units.

According to the present invention there is provided a i load supporting unit comprising a hollow member having two opposed end faces, an extensible wall connecting the end faces to form a closed space and permit the distance between the end faces to vary, means defining Ia cupshaped cavity on one of the end faces on the side thereof outside the closed space and including a rim for cooperation with a supporting surface or the load and to define a restricted fluid escape gap between the rim and the surface or load, flow restricting inlet means for connecting a supply of pressurised fluid to said closed space, and flow restricting outlet means connecting said closed space to the interior of said cup-shaped member. In one particular form, part of the unit may 4be attached to the load, the rim may rest upon the ground, and the pressure fluid reaching the cup via the two orifices will ll the chamber and form a cushion in the cavity to support at least part of the load.

In one form of construction, the chamber is a bellows with substantially inflexible top and bottom walls. The inlet orifice is in one -of these walls and the outlet in the other and the bellows is coaxial with the cup-shaped cavity. Other forms of construction can however :be used. The rim may be of resilient construction and preferably is supported so that its resilience in a radial direction is restricted.

The invention also includes the combination of at least three load supporting units, preferably fed by the same pressure source, and mounted on a common platform on which the load can rest. For stability the units, when viewed in plan, should not lie along a single straight line. For convenience the embodiments of the invention described herein will be those in which a load is carried by one or more supporting units, for movement over a surface, the cushion of pressurised fluid 'being formed between the unit, or units, and the surface. It will be appreciated that load supporting units according to the present invention can be used the other way up, for example resting on a surface and the cushion of pressurised fluid being formed between the unit, or units, and the load, whereby the load can move relative to the unit or units.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which:

FIGURE l is a vertical section through a load supporting unit,

FIGURE 2 is an elevation of a load carrying platform comprising six units mounted in common,

FIGURE 3 is an inverted plan of the platform illustrated in FIGURE 2,

FIGUREv 4 is a vertical section similar to FIGURE 1 illustrating a modilication thereof, and

3,267,882 Patented August 23, 1966 Mice FIGURE 5 is a further vertical section similar to FIG- URE 1 illustrating another modification thereof.

The unit illustrated in FIGURE l comprises a bellows 1 with flexible side walls 2, a top end plate 3 .and a bottom end plate 4. An inlet orifice 5 in the top end plate 3 communicates with a pressure source 6. The bottom end plate 4 also constitutes the base of a cupshaped cavity 7. Angled tie-strings 9 prevent undue axial separation, sideways movement, or relative rotation of end plates 3 and 4. A flexible annular member 8 with a rounded rim 11 is bonded to the periphery of the underside of the bottom plate 4 and constitutes the wall of the lcup-shaped cavity 7. An outlet orifice 10 is formed in the plate 4. Fluid can pass from the source 6 through the inlet orifice '5 to the interior of the bellows 1 and thence through the outlet orifice into the interior of the cavity 7.

In operation, fluid is -fed from the pressure source 6, flowing through the inlet orifice 5 into the interior of the Ibellows 1. From the interior of the bellows, the fluid flows through the outlet orifice 10 into the interior of the cavity 7. A pressure balance is set up across the bottom end plate 4 and normally a small clearance exists between the rim 11 of the member 8 and the surface 12, excess fluid escaping through this clearance. The pressure within the bellows is such that, when acting over the larea of the top end plate 3, it will support the load carried or supported by the unit. Similarly, the pressure within the cavity 7, is such that, when acting over the effective area of the cavity, it will balance the pressure in the bellows acting over the effective area of the bellows. The inlet orifice S, outlet orifice 10 and the clearance between the rim 11 and the surface 12 act as a series of metering -or control orifices in that any variation of the clearance between the rim 11 and the surface 12 will initially produce a corresponding pressure variation inside the cavity which will cause the bottom end plate 4, with the annular member 8, to move so as to restore the clearance. Eventually the pressures within the cavi-ty and the bellows will settle at a new pressure balance. This arrangement provides particular advantages when a series of units are used together as will be described later. It will be appreciated that the pressure at the pressure source 6 must be equal to or a'bove the maximum pressure which is likely to occur within the bellows.

FIGURES 2 'and 3 show how six cells'may conveniently be mounted on a common loadcarrying platform 15. The pressure `source 6 can be mounted on the platform also but conveniently can be mounted elsewhere and connected to the platform by way of a flexible lead 16. A plenum chamber 17, of large volume relative to each of the bellows 1, is formed as part of the platform 15, the individual units being fed :from the plenum chamber. The purpose of the chamber 17 is to supply pressure fluid easily at substantially equal pressure to all six inlet orifices. As described above with reference to FIGURE 1, a balance is always maintained between the forces lacting on opposite faces of the bottom end plate 4 of each unit. Should the platform pass over small-scale undulations in the surface, these will be accommodated by the flexible members 8 of the individual units, without causing substantial changes in any of the pressures within the cupshaped members Ior bell-ows. However, the undulations of the surface may be more substantial. The situation will now be considered in which a platform is moving over such a surface and one of the units comes into register with a dip while the Iothers all regi-ster with parts at the normal level. Initially, the clearance between the surface and the rim 11 of the odd unit will increase. The mass flow of fluid through the clearance will therefore increase with a resulting decrease in the pressure within its cavity. There will thus be an unbalance of pressure -across the bottom end plate and .these unbalanced forces `on the bottom plate 4 cause the bellows to expand. Equilibrium will 'be restored with the clearance, and the pressures, much as before but the bellows expanded to bridge the greater gap between the platform and the surface. The attitude of the platform therefore does not change. Reverse operation will occur when one or more units encounter a local raising of the surface, such as a bump.

Other situations may arise in which the individual units react to prevent movement of the platform. For instance, the load upon the platform may change so as to increase the load bearing on one particular unit. This will tilt the platform and cause the clearance between that unit and the surface to decrease, with an accompanying decrease in mass flow through this clearance and increase in pressure within the cavity. The pressure increase within the cavity will reduce the mass ow through the outlet orifice 10 thus raising the pressure within the bellows. The `bellows will extend until eventually the platform is level, the increased pressures acting within the particular unit being increased to support the increased load. Reverse operation of a unit, or units, will occur should the lo-ad carried by a particular unit, or particular units, decrease.

FIGURE 4 illustrates a modification of the unit illustrated in FIGURE 1. The annular member of FIG- URE 1 is replaced by a moulded member 2f? which gives a higher degree of resistance to -sideways deflection of the rim 11 than the construction of FIGURE 1.

A further modification of the unit illustrated in FIG- URE 1 is illustrated in FIGURE 5. In this arrangement the flexible bellows 2 of FIGURE 1 is replaced by lcoaxial sliding tubes 23 and 24. The -outer surface of the inner tube 23 and the inner surface of the -outer tube 24 can cooperate so as to substantially prevent escape of fluid from inside the tubes. As an alternative a sealing strip can be attached to one tube and held in contact with the other as indicated at 25. Means, such as ties 26, can be provided to limit the downward movement of the inner tube 23. An arrangement as illustrated in FIGURE 5 is particularly useful when only small variations in height of the load relative to the surface have to be accommodated.

The units can be of any suitable cross-section, when viewed in plan, `but generally circular cross-sections are preferred. However, it will be appreciated that other shapes may be more efficient such as when it is desired to make the units cover the maximum possible area of a platform.

The construction of the annular member 8, or the member 20, can vary considerably. Resilient material such as foamed rubber or suitable synthetic material can be used. As an alternative an inflated construction can be used. A further alternative comprises a flexible torus partially filled with a liquid but without any gas space. To assist in reducing friction between the rim 11 and the surface 1.2 should contact occur, the rim can be coated with a friction reducing material, such as polytetrafluorethylene.

A unit, or a platform including a number of units, according to the invention, can be positioned under a load which is supported on a pallet or some similar device, with the pressure supply turned off. When the pressure supply is turned on, the hollow member, eg., the bellows or coaxialV sliding tubes, extends to lift the lo-ad. After the load has been moved, the unit or platform can readily be removed from beneath the load by shutting off the pressure supply, allowing retraction of the hollow member due to the decrease in pressure therein as the load forces fluid out of the member through the outlet orice after the supply of pressurised fluid lto the inlet orifice h-as been shut off.

We claim:

1. A load supporting unit comprising a hollow member having two opposed end faces, an extensible wall conineoting the end faces to form a closed space and permit the distance between the end faces to vary, means defining a cup-shaped cavity on one of the end faces on the side thereof outside the closed space and including a rim for cooperation with a supporting surface or the load, flow restricting inlet means for normally supplying an un- Y interrupted flow of pressurised fluid to said closed space,

and flow restricting -outlet means connecting said closed space to the interior of said cup-shaped cavity through which the fiuid .supplied to Said closed sp-ace normally flows into said cavity to form a cushion of pressurised fluid therein effective to maintain a restricted fiuid escape gap between said rim and the surface or load.

2. A load supporting unit as claimed in claim 1 wherein the wall connecting the end faces is of flexible material.

3. A load carrying unit as claime-d in claim i wherein the wall connecting the end faces comprises two cooperating tubes capable of sliding one within the other.

4. A load carrying unit as claimed in claim 1 wherein the means defining the cup-shaped cavity comprises an annular member attached to said one end face.

5. A unit as claimed in claim 4 wherein the annular member is flexible.

6. A unit as claimed in claim 5 wherein the annular member comprises a member having greater resistance to deflection in a direction parallel to the said end face than in a direction normal to said end face.

'7. A unit as claimed in claim 1 including means for limiting the variation of the distance between the end faces.

8. A load supporting device including a platform, and at least three load supporting units mounted on said platform, each unit comprising a hollow member Ihaving two opposed end faces, an extensible wall connecting the end faces to form a closed space and permit the distance between the end faces to vary, means defining a cupshaped cavity on one of the end faces on .the side thereof outside the closed space, and including a rim for cooperation with -a supporting surface or the load, flow restricting inlet means for normally supplying Ian uninterrupted flow of pressurised fiuid to said closed space, and flow restricting outlet means connecting said closed space to the interior of said cup-shaped cavity through which the fluid supplied to said closed space normally flows into said cavity to form a cushion of pressurised fiuid therein effective to maintain a restricted liuid escape gap between said rim and the surface or lo-ad.

9. A load supporting unit comprising a hollow member having two opposed end plates, an extensible wall of flexible material connecting the end plates to form a closed space and permit the distance between the end plates to vary, means comprising an annular member attached to one of the end plates dening a cup-shaped cavity on the side of said end plate outside the closed space, said annular member being flexible and including a rim for cooperation with a supporting surface or the load to be supported, flow restricting inlet means for normally supplying yan uninterrupted flow of pressurised fluid to said closed space, flow restricting outlet means connecting said closed space to the interior of said cupshaped cavity through which the fluid supplied to said closed space normally fiows into said cavity to form a cushion of pressurised fluid therein effective to maintain a restricted fluid escape gap between said rim and the surface or load, and means for limiting variation of the distance between the end plates.

l0. A load carrying device including a platform adapted to support a l-oad on its upper surface, and at least three load supporting units connected to and depending downwardly from said platform, each unit comprising .a hollow member having top `and bottom end plates, an extensible wall of flexible material connecting the end plates to form a closed space and permit the distance between the end plates to vary, means comprising an annular member `attached to the bottom end plate defining a cup-shaped cavity on the side of said end plate outside the closed space, said annular member being flexible and including a rim for cooperation with a supporting surface, iiow restricting inlet means for normally supplying yan uninterrupted fiow of pressurised fluid to said closed space, flow restricting outlet means connecting said closed space to the interior of said cupshaped cavity through which the fluid supplied to said closed space norm-ally flows into said cavity to form a cushion of pressurised fluid therein effective to maintain a restricted fluid escape lgap lbetween said rim and said supporting surface, and means for limiting variation ofthe distance between the end plates.

References Cited by the Examiner UNITED STATES PATENTS 6 Canfield 254-93 X C-olbridge 24S-188.9 Thompson 267--65 Evans 24S- 188.9

Hansen et al 280--124 Faiver 280-124 Arenson 24S-188.9

Cislo 62-156 Patchen 254--93 Billrnan 180-7 Bertin 254-93 15 FRANK B, SHERRY, Primary Examiner.

J. T. MCCALL, Assistant Examiner. 

8. A LOAD SUPPORTING DEVICE INCLUDING A PLATFORM, AND AT LEAST THREE LOAD SUPPORTING UNITS MOUNTED ON SAID PLATFORM, EACH UNIT COMPRISING A HOLLOW MEMBER HAVING TWO OPPOSED END FACES, AN EXTENSIBLE WALL CONNECTING THE END FACES TO FORM A CLOSED SPACE AND PERRMIT THE DISTANCE BETWEEN THE END FACES TO VARY, MEANS DEFINING A CUPSHAPED CAVITY ON ONE OF THE END FACES OF THE SIDE THEREOF OUTSIDE THE CLOSED SPACE, AND INCLUDING A RIM FOR COOPERATION WITH A SUPPORTING SURFACE OR THE LOAD, FLOW RESTRICTING INLET MEANS FOR NORMALLY SUPPLYING AN UNINTERRUPTED FLOW OF PRESSURISED FLUID TO SAID CLOSED SPACE, AND FLOW RESTRICTING OUTLET MEANS CONNECTING SAID CLOSED SPACE TO THE INTERIOR OF SAID CUP-SHAPED CAVITY THROUGH WHICH THE FLUID SUPPLIED TO SAID CLOSED SPACE NORMALLY FLOWS INTO SAID CAVITY TO FORM A CUSHION OF PRESSURISED FLUID THEREIN EFFECTIVE TO MAINTAIN A RESTRICTED FLUID ESCAPE GAP BETWEEN SAID RIM AND THE SURFACE OR LOAD. 